How can we prepare for worst-case-scenario storms when climate change means we can’t accurately predict what the worst-case scenario is?

​The audience at the Provincial Flood Forecasting and Warning Workshop sat silently as the rug was pulled out from under them.

Municipal and provincial staff — many of them forecasters and emergency managers — were gathered at a Brampton conference centre to hear Gord Miller, Ontario’s former environmental commissioner, talk about climate change. What he had to say challenged many of the established practices and assumptions that had guided their careers.

His point was this: climate change has altered the fundamentals of the weather system. All of our old predictions — which were used to build thousands of kilometres of road, drainage pipe, and sewers — are inadequate. The changes to the weather system are so profound that old models and methods can’t accurately predict what’s going to happen; new models predict catastrophes so great that preparing for them could lead to bankruptcy.

“I don’t think here in Canada we understand what’s coming,” said Miller during the talk. “We have no predictability any more. One has to look from the perspective that all culverts are undersized. All sewers are undersized.”

When the floor at the convention centre was opened for questions, it took a moment before the crowd was ready to ask any. They trickled in slowly. One man noted that Hurricane Hazel — the 1954 storm that ripped across southern Ontario, leading to 81 deaths and millions of dollars in property damage — has guided the development of Toronto’s floodplain maps and infrastructure decisions ever since. Surely that would prepare the city for what was to come.

Miller pointed to the example of Hurricane Harvey, a storm that devastated Houston in August 2017. Climate change almost certainly made it more intense. Severe storms will be more intense now than they were in 1954.

Paulin Coulibaly, scientific director of FloodNet, a research consortium tackling the problem of flooding, agrees: the storms we’re facing are unlike anything that’s come before in terms of intensity and duration.

“We were relying on the historical information. Now we cannot rely on the historical information, because it is not enough to tell us what will happen in the future,” says Coulibaly. “We have to rely on future information.”

Researchers rely on climate-change projections, which vary wildly because of the complexity of the science and the lack of certainty over how much the world will reduce its carbon emissions. Coulibaly and his team are tackling the difficult task of adapting those projections into data that can guide infrastructure decisions — a process where small variations can cost millions of dollars.

* * *

Carol Solis lost everything in the flood.

It started with six inches of sewage in her basement in May 2014. And that was just the start of her problems. After the mess was cleaned up, she went on vacation; while she was away, the August 2014 storm brought 24 inches of sewage into the basement of her Burlington home, ruining thousands of dollars in clothes and possessions.

She was able to recoup some of the value of her lost possessions, but the claims process was long and arduous: the insurance paperwork took nearly two years to complete.

A storm in August 2014 brought 24 inches of sewage into the basement of Carol Solis’s Burlington home.

“It's bad enough to have a sewage flood, but the aftermath — people don't realize unless they've gone through this. I've had a business for years in marketing and training, and I was taken away from my business to do this, because I had to do proof of loss for the insurance company, in the meantime just trying to wrap my head around the fact that I've lost 80 per cent of my whole life belongings,” says Solis.

More than 6,000 homes were damaged during the storm. The City of Burlington was forced to grapple with just how something like this could have happened.

“We use the same old infrastructure that our parents did — the ’50s, ’60s and ’70s, we're still on that infrastructure,” says Dave Phillips, senior climatologist with Environment Canada.

The limits of flood plans, though, were also revealed. Many infrastructure designs, including those in Burlington, are based on a 100-year storm scenario that involves 99.8 millimetres of rain in 10 hours — but that August, 191 millimetres of rain fell in the course of 10 hours on just one area of the city. The storm was less like their worst-case scenario, and more like Hurricane Hazel — a weather event so devastating, the name was retired.

The 60-minute intensity of the cell, measured by radar, was 56 millimetres per hour — Hazel's was 53 millimetres per hour. The 2014 event dumped 170 millimetres in seven hours over 25 square kilometres, according to a report from Conservation Halton; Hurricane Hazel brought 212 millimetres in 12 hours. Although its area and duration were much smaller, the 2014 Burlington event was, at its peak, more intense than Hazel.

Hazel, Miller says, was a major hydrologic event “from a period of time, from a climate that we no longer have.”

“The hurricanes are more severe than they’ve ever been before, and severe hurricanes are occurring more frequently. One of them will go up the Mississippi Valley and hit southern Ontario, and almost certainly, it'll be worse than Hurricane Hazel.”

There is a wide consensus that climate change is affecting extreme weather, but the connection is still being investigated, so it’s tricky to predict weather effects with accuracy. Global climate-change models provide the best information, says Coulibaly, but scaling them down to the local level introduces uncertainty.

“The predictions are not perfect — they're not good enough,” says Coulibaly. “The changes in the precipitation for 2020, 2030, 2050 will not be the same depending on how we behave today. If we do nothing, what we see in 2030 will be different.”

In 2005, Coulibaly and Xiaogang Shi, a hydrology researcher, were asked to study highway drainage in Ontario and evaluate how it would be affected by the increased rainfall associated with climate change.

Using global climate models downscaled to the local level, the pair produced a report that recommended that the diameter of all drainage pipes and sewers be increased by 16 per cent (for reference, a toonie is about 17.5 per cent bigger in diameter than a quarter).

“They did the calculation internally about how much it would cost them. They didn't tell me the number, but they were very, very concerned about the cost,” says Coulibaly. “If you look at the number of structures they have to replace or upgrade, it's huge. In general, people see a change of 10 or 15 per cent. It's not adding 10 or 15 per cent of the money — a 10 per cent change can cost you close to 40 to 45 per cent more money.”

In other words: increasing the capacity of our storm infrastructure will break budgets that are already broken. Coulibaly and Shi’s report recommended that all drainage infrastructure be increased across a province that already has an infrastructure deficit.

Much of the province’s infrastructure falls under the jurisdiction of municipalities. In 2008, municipalities across Ontario came together to evaluate the state of their infrastructure — things like drinking water, sewage and waste disposal, roads and bridges, and public transit. They estimated that the total infrastructure deficit, based on infrastructure at the end of its lifecycle, was roughly $60 billion. That number hasn’t been comprehensively updated, but while there has been some investment, Pat Vanini, executive director of the Association of Municipalities Ontario, says, it falls well short of what’s needed.

“There's progress, but we're not eroding enough of that gap,” says Vanini. “If you can't do the maintenance, it's like if you're doing your roof — you know what the asset's worth to replace it, but if you let it slip and you let the ice build up or the leaves gather in the gutters, all that makes the life expectancy of the roof less.” This past spring and summer were difficult for Ontario municipalities. Heavy rains flooded roads and bridges, damaging infrastructure and adding to that tally.

“I know when I was travelling the province, the number of roads and culverts that were washed out in rural Ontario was significant. That in itself would add even more burden, because those weren't necessarily anticipated events,” says Vanini.

Miller argues that we need to assume that all predictions are inadequate if we’re serious about preparing for climate change.

What he’s arguing will mean a seismic shift for cities everywhere. Infrastructure decisions are based on forecasting years into the future, but dramatic weather changes mean those forecasts are based on assumptions that are no longer sound. But to accept this would mean acknowledging that the work done thus far has been inadequate, and that projects currently underway are based on flawed premises. Miller suggests that in addition to designing for bigger storms, we need to expect that infrastructure will fail: buy generators to cope with power outages, purchase boats to cross flooded roads, and use sandbags to keep out advancing waters.

* * *

Researchers are still investigating how climate change is affecting storms. Temperature plays a role — each degree of warming increases air’s water capacity by 7 per cent. And the jet stream — high-level currents that encircle the Earth and carry weather systems — is changing in ways that are still being studied. Jet streams are high-altitude currents that move weather systems across the map. Sometimes, they are straight and fast; other times, they are slow and wavy. During slow and wavy periods, weather systems tend to linger, bringing long droughts or periods of heavy rainfall.

“What is changing is we're seeing those wavy patterns more often now. They're not something new — it's just that we're seeing a change in the frequency of those kinds of patterns,” says Jennifer Francis, a researcher with the Rutgers University department of marine and coastal sciences.

“Most of our infrastructure has been built to accommodate the kind of conditions that we've been used to for the last several decades. That might be the size of pipes used to drain stormwater from the street. They're just too small now, because we know that we're getting heavier downpours. When it does rain, it tends to rain harder,” says Francis.

Another significant factor is the role played by human development, which has decimated wetlands in Ontario. For example, in Toronto, Ashbridge’s Bay — formerly a large wetland on Lake Ontario — was paved over in the early 20th century to make way for industrial development.

“We think prosperity is paving it over and cementing it,” says Phillips. “That raindrop that falls on a very dry Hamilton or a very dry Toronto becomes a flood drop because it falls on a hard surface.”

Hurricane Hazel caused so much damage largely because rivers overtopped banks, and homes were built on floodplains then, says Phillips. Today, storm damage is generally the result of overloaded infrastructure — drainage pipes that aren’t big enough, water treatment plants stretched to capacity, and sewers that overflow. Concentrated, slow-moving storms are more likely to overwhelm such systems.

That’s just what happened in Solis’s basement, when raw sewage backed up as a result of torrential rains. There are devices, like sump pumps and backflow valves, that can help alleviate flooding, but those were not typically installed in older homes like hers, Solis says.

“Inadequate funding has created a $6.8 billion stormwater infrastructure deficit in Ontario. This financial gap could get even bigger in the future as population growth leads to the creation of more impermeable surfaces and, consequently, worsens runoff,” reads a 2016 report from the Environmental Commissioner of Ontario.

Indeed, much of the infrastructure in the province has reached the end of its design life, Coulibaly says.

“In Canada, we're on the crossroads because most of the infrastructure is outdated,” he says. “Most of them were designed a long time ago — more than 50 years. They're up for replacement, and we're at the time that replacement means we replace them with a different design number. That means bringing the cost up by 25, 30 — some people say up to 50 per cent more. It's a tough decision to make, but it's not a decision we can hide from.”

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